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How do you ground a building that has been electrically isolated by means of seismic isolators?

Hi Davut,

Thank you for your question regarding building grounding with seismic isolators, it is our pleasure to help.

When you have a building constructed with a seismic base, your foundation should be considered to be isolated.  This would fall in to the same category of building as one that has a vapor barrier between the concrete foundation and the earth.  In these cases, you may not use building steel as a grounding electrode. 

Now, you still need to bond to building steel and make all the same connections to the frame as required under normal regulations.  You simply must have a dedicated grounding electrode for the building.  Frankly, E&S Grounding Solutions recommends this arrangement for all buildings.  While most electrical codes and regulations allow the use of building steel as an electrode, we don’t recommend using it.

Keep in mind, there is a big difference between “Bonding” to an item, and using it as an “Electrode”.  Understanding this difference is very important.  Consider gas-pipes for example.  Your gas-pipes must be bonded to ground to prevent any hazardous differences in potential from forming, but you sure don’t want to force electrical energy down them by using them as a grounding electrode.

As far as designing a grounding system goes, it is difficult to know what to design when we don’t know what you are grounding.  Are there high-voltage transformers inside, do you have an electronic data center, a lighting protection system, what specifications need to be met?  You may need a ground ring that surrounds the entire building, maybe you need a deep-earth grounding electrode, or perhaps just a series of simple grounding rods.

Whatever you end up designing you should ensure that the connections from the grounding electrode system back into the building are made using flexible grounding straps.  You should Google up gate grounding straps for an example of flexible grounding straps.  There are a number of companies that sell these type of products.

We hope this helps you, if you should have any further questions, please do not hesitate to contact us again.

Best regards,

The Engineering Team at E&S Grounding Solutions

 

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